Coupled analysis and performance evaluation of a semi-submersible floating wind turbine with active ballasting system

Abstract

Semi-submersible floating offshore wind turbines (FOWTs) are susceptible to platform inclination induced by wind thrust, which amplifies motion responses, reduces power generation efficiency, and compromises structural safety. To mitigate these challenges, an active ballasting system (ABS) can be introduced to dynamically redistribute the ballast water within the platform. A fully coupled aero-hydro-servo-elastic model is developed in SESAM, where the effects of ballast water movement are represented by applying external moments to the platform. Real-time interaction between the floating structure and the active ballasting program is established via TCP communication. The program, implemented in Python, employs a PID control algorithm based on platform pitch and roll angles, while incorporating pump flow constraints. The IEA 15 MW floating wind turbine is selected as the reference model. The coupled model is validated by comparing the motion responses of the FOWT without active ballasting against published benchmarks. Additionally, computational fluid dynamics (CFD) simulations are carried out to investigate the hydrodynamic behavior of the FOWT under both upright and inclined conditions. The active ballasting system is then applied in time-domain simulations under a range of environmental conditions. Simulation results demonstrate that the average inclination is reduced to near-zero, while the mean power output is improved under identical operating scenarios